Solidification structures of Bi-Mn alloys solidified in a magnetic field up to 10 T were investigated experiemtaliy. The solidification of the alloy from melt or semisolid in the magnetic field was carded out. The alignment-retaining behavior of the alignment of BiMn structure during reheating of the alloy, which was obtained by solidification in the magnetic field, was also investigated. It was found that with different temperatures of starting solidification the structures were varied, namely, in the temperature zone below Curie point a rod-like BiMn gains appeared, in the zone above Curie point and below the liquidus a flake-like BiMn grains appeared, and in the case of completed melt tightly piled flake-like BiMn grains were produced. In all these cases, the grains were aligned and orientated with 〈 001 〉 along the direction of the field. When the alloy with rod-BiMn grains was reheated to below Curie point, the alignment of the BiMn was kept, while reheated to above Curie point, the alignment was destroyed.
The solidification structure of Bi-3 wt pct Mn alloy grown up in the semisolid zone under the influence of a staticmagnetic field (up to 1.0 T) and the relation of the magnetic property with the solidification structure have beeninvestigated experimentally. It was shown that the primary phase MnBi crystals in the alloy aligned and oriented alongthe direction of the applied magnetic field. The orientating tendency and the average length of the elongated MnBicrystals increased with the increase of the applied field and the solidification time. Moreover, the remanence of thealloy along the aligned direction of the MnBi phase in the case of solidification with a magnetic field was apparentlyanisotropic and nearly double of that without the magnetic field. This indicated that the MnBi crystals orientedand aligned along their easy magnetization axis. A model was proposed to explain the alignment and orientationgrowth of the MnBi crystals in a magnetic field in terms of the magnetic anisotropy of the crystals and the magneticinteraction between them.
